Method of treating pentachlorophenol

ABSTRACT

METHOD OF TREATING PENTOACHLOROPHENOL FLAKES, PELLETS OF PRILLS WITH AN OIL AND A GLYCOL TO PREVENT FORMATION OF DUST DURING STORAGE.

United States Patent O 3,692,561 METHOD OF TREATING PENTACHLOROPHENOL Frederick M. Hager, Elmira, Waterloo, Ontario, Canada, assignor to Uniroyal Ltd., Montreal, Quebec, Canada No Drawing. Filed June 29, 1970, Ser. No. 50,891 Int. Cl. B44d 1/02; C09k 3/22 US. Cl. 117-100 A Claims ABSTRACT OF THE DISCLOSURE Method of treating pentachlorophenol flakes, pellets of prills with an oil and a glycol to prevent formation of dust during storage.

The present invention relates to a method of treating pentachlorophenol in order to substantially reduce the formation of dust on the surface of this material.

Pentachlorophenol is well known as a fungicide. One of its major commercial uses is in the treatment of wood to preserve it against attack by fungi and particularly by soil-borne organisms. It is generally sold in the form of flakes, pellets or prills (i.e. small beads). When freshly prepared, the pentachlorophenol is free of dust, but during storage the material becomes progressively more coated with dust. It is believed that this dust is a result of the natural tendency for pentachlorophenol to sublime. As a result of this tendency, very fine crystals form on the surface of the pentachlorophenol; after a few weeks the accumulation of fine crystals on the pentachlorophenol resembles cotton. When the containers of pentachlorophenol are emptied at the time of use, the fine crystals are dispersed in the air as a dust, and are highly irritating to the eyes, nose and throat. Because of the toxic nature of pentachlorophenol, inhalation of this dust should be avoided.

Numerous methods have been used or proposed in an attempt to suppress or eliminate the formation of this dust. Pentachlorophenol is usually treated with a small amount of petroleum oil, which treatment provides a slight retardation of the formation of dust. Special physical forms, e.g. prills or pellets, have been used, but this method provides no long-lasting benefits and has a further disadvantage in that it requires special, expensive processing equipment. In Canadian Pat. 749,423 flaked pentachlorophenol is contacted with hot air to provide a.

glazed surface on the flakes. The disadvantages noted and discussed above are also applicable to this method of treatment.

F The present invention resides in a novel method of treating pentachlorophenol with both an oil and a glycol so that little or no dust is formed, even on extended storage. This method is convenient, requires no expensive equipment, and provides the desired benefits at low cost. Because flaked pentachlorophenol is the most convenient and least expensive form to produce, the description herein is mainly in terms of this form; however, other forms may be treated using the method without departing from the intent or scope of the invention.

The oil used in the method may be any of the wide range of petroleum oils. For convenienece in handling and application, oils having relatively low viscosity are desirable, but more viscous oils may be used without re ducing the effectiveness of the method. If oils of high viscosity are employed, it may be found convenient to heat these oils to reduce their viscosity at the time of application. Diesel fuel oil which has a viscosity of about 3.3 centistokes at 100 F. is effective, easy to apply, low in cost, and is therefore a preferred oil to be used. Lubricating oil having a viscosity rating of S.'A.E. 40, or S.S.U. 700 at 100 F., has also been used. Very ice heavy oils having a viscosity of S.S.U. 5000 at F. may also be used, but as noted above, it will be desirable to heat such oils at the time of application, in order to reduce their viscosity. In addition to petroleum oils, vegetable oils such as palm oil, cottonseed oil, linseed oil, corn oil and the like may be used with satisfactory results.

Any of the common liquid glycols, e.g. ethylene glycol, propylene glycol, diethylene glycol, glycerol, butylene glycol and polyglycols of even higher molecular Wight may be used as the glycol component. Even viscous liquid or waxy polyglycols of molecular weight up to 4000 or even higher, may be employed if they are heated to make them fluid, or if they are dissolved in water to obtain a solution of low viscosity. It has been found advantageous to premix even the lower glycols such as ethylene glycol and propylene glycol, with water. Generally the preferred ratio is between 0.01 and 10 parts of water admixed with one part of glycol.

It is preferred to apply the oil and the glycol by means of a spray, although other suitable application means can be used. The spraying may be done in a simple ribbon blender, or in other mixing devices which are well known to specialists in the art. The objective is to obtain a uniform coating of the pentachlorophenol and to reduce the possibility that some of the pentachlorophenol will not be coated. The glycol or glycol-water solution may be applied onto the pentachlorophenol using the same equipment used for the oil treatment or using a different piece of equipment, as desired. With suitable equipment both spraying operations may be done in a continuous manner rather than batch-Wise; however, variations of these procedures may be employed without departing from the scope of the invention.

The treatment with oil may either precede or follow the treatment with glycol as both orders of application have given satisfactory results. The treatment of the pentachlorophenol with the second agent is normally done immediately after the treatment with the first agent. Alternatively, both agents can be sprayed concurrently onto the pentachlorophenol. If separate treatments are employed, it is desirable that the second treatment be done within a few days of the first treatment. Pentachlorophenol which has been treated with only one of the agents will begin to sublime within a Week, and the value of the second agent is reduced.

The amounts of oil and of glycol may be varied within broad limits. However, it is recognized that because pentachlorophenol is generally sold on the basis of purity or assay, excessive amounts of additives are undesirable. Indeed, from a commercial viewpoint, the usual objective will be to employ the minimum amounts of additives which will provide the desired benefits. Also, the use of excessive amounts can cause the flakes of pentachlorophenol to adhere to processing equipment or to each other and build up lumps. Thus, one may use as much as a total of 8 parts of oil and glycol per 100 parts of pentachlorophenol, but quite satisfactory results are obtained with as little as a total of 1.5 parts of oil and glycol per 100 parts of pentachlorophenol. In any case, at least about 0.5 part of either oil or glycol should be included in the total. In order to ensure adequate coverage of the flakes and in order to provide long-lasting inhibition of sublimation or formation of dust, it is preferable to use about 2 parts of oil and 1 part of glycol per 100 parts of untreated pentachlorophenol.

In the examples which follow, technical grade pentachlorophenol having an assay of 97%, in the form of fiat flakes having an average thickness of about 0.03 inch was employed. The flakes were irregular in shape but roughly had a diameter of from about A; inch to about inch.

The flakes were sprayed with the first agent in a laboratory mixer and later in the same day were sprayed with the second agent in the same laboratory mixer. The laboratory mixer used was a twin-cone blender.

The treated pentachlorophenol was stored in covered glass jars; at the same time, untreated pentachlorophenol was put in a similar jar, for comparison. The treated and untreated pentachlorophenol in every case was subsequently examined and rated according to the following schedule:

RATINGS 10=large amount of sublimate. Very unsatisfactory. 5=moderate amount of sublimate. Unsatisfactory. 3=slight amount of sublimate. Tolerable.

2=no distinct sublimate but flakes appear dusty. 1=fla=kes have a dull appearance. Look dry. =fiakes are smooth. Look as if they were damp.

In the examples which follow, the amounts of the agents used were per 100 parts by weight of untreated pentachlorophenol.

EXAMPLE 1 Pentachlorophenol flakes were treated first with diesel fuel oil, which had a viscosity of 3.3 centistokes at 100 F.; then with a glycol or glycol admixed with water as described in Table 1. After 30 days storage, ratings of dustiness were made, and the results are given in Table I.

TAB LE I Ethylene Propylene Oll glycol glycol Water Rating From the above results it will be seen that the combi nation of oil plus glycol provides a definite inhibition of formation of dust, whereas oil alone or glycol alone is unsatisfactory.

EXAMPLE 2 In order to ascertain the effect of the order of treatment, the following experiments were performed: in the tests of Series 1, the oil treatment was done first; in the tests of Series 2 the oil treatment followed the treatment with glycol or glycol plus Water. Ratings were made after 30 days storage. The results are given in Table II.

TABLE II Diesel Ethylene Propylene oil glycol glycol Water Rating From this data, it will be seen that the benefits obtained by the invention are not dependent upon the order of treatment.

EXAMPLE 3 Pentachlorophenol flakes as described previously were treated first with one of the oils listed, followed by a treatment with the glycol admixed with water. Ratings were made after the indicated number of days. The results are given in Table III.

TABLE III A B C D E F G H I J K Diesel oil 2 2 2 2 2 2 2 2 2 2 2 Ethylene glycol 1 Diet-hylene glycol 0.5 l

Propylene glycoL Dipropylene glyc 1,3-butylene glycol. Carbowax 1000 Glycerol 1 Water 1 0.5 1 0.5 1 0.5 l 0.5 0.5 l Rating, days:

L M N O P Circo light process all 2 Ethylene glyeol- 1 1 1 1 1 Water 1 1 1 1 1 Rating, days:

From the data presented above, it is obvious that a variety of oils and a variety of glycols may be used according to the invention to obtain a satisfactory reduction of the dust which forms on pentachlorophenol.

Having thus described the invention, what is claimed and desired to be protected by Letters Patent is:

1. A method of treating pentachlorophenol flakes, pellets or prills to reduce the formation of sublimate crystals or dust thereon during storage, comprising applying to the surface of pentachlorophenol particles an efiective amount of a combination of a first agent selected from the group consisting of petroleum oils and vegetable oils, and a second agent selected from the group consisting of glycols, polyglycols and glycerol.

2. The method of claim 1 wherein one part of the second agent is admixed with between about 0.01 and 10 parts of water prior to its application to the pentachlorophenol.

3. The method of claim 1 wherein at least 0.1%, based upon the weight of pentachlorophenol, of said first and second agents are applied to the surface of said pentachlorophenol.

4. The method of claim 3 wherein said second agent is mixed with water at the ratio of from 1:0.01 to 1:10 respectively prior to its application to said pentachlorophenol.

5. The method of claim 3 wherein the treatment with the first agent procedes the treatment with the second agent.

6. The method of claim 3 wherein the treatment with the second agent precedes the treatment with the first agent.

7. The method of claim 3 wherein the first agent and the second agent are applied to the pentachlorophenol by means of a spray.

8. The method of claim 3.wherein the first agent and the second agent are applied to the pentachlorophenol in a mixing device.

9. The method of claim 3 in which the first agent is a diesel fuel oil.

10. The method of claim 3 in which the second agent is ethylene glycol.

11. The method of claim 3 in which the second agent is propylene glycol.

12. The method of claim 3 in which the treatment is performed in a continuous operation.

13. The method of claim 4 wherein the treatment with the first agent precedes the treatment with the second agent.

14. The method of claim 4 wherein the treatment with the second agent precedes the treatment with the first agent.

15. The method of claim 4 wherein the first agent and the second agent are applied to the pentachlorophenol by means of a spray.

16. The method of claim 4 wherein the first agent and the second agent are applied to the pentachlorophenol in a mixing device.

17. The method of claim 4 in which the first agent is a diesel fuel oil.

18. The method of claim 4 in which the second agent is 15 ethylene glycol.

19. The method of claim 4 in which the second agent is propylene glycol,

20. The method of claim 4 in which the treatment is performed in a continuous operation.

References Cited UNITED STATES PATENTS 2,944,936 7/1960 Bronson 424347 2,150,786 3/1939 Schmitt 117100 A 3,085,047 4/1963 Weinert 117-100 A 3,053,730 9/1962 Winbladh 424347 3,011,940 12/ 1961 Bollenback 260623 R 3,321,298 5/1967 Bidlack et a1 117100 A 2,465,346 3/1949 Bodman 117100 A WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner US. Cl. X.R 117-147; 42 347 

